There are Princo's & there are Princo's .... not all are the same (unlike Riteks).
Datawrite Red Tops started out good, then they changed the dye on subsequent batches, which made them useless. Most reputable suppliers in the UK are not stocking them now ... I guess they'r pi**ed off with all the returns.
Not all Princos are bad, but they are not consistent .... i.e. what works today doesn't work when a new batch arrives. Most people find this out the hard way and progress to Riteks. They are a little more expensive, but it's worth it, to lose all the aggro.